Polyvinyl chloride (hereinafter referred to as “PVC” for short), one of the varieties having the largest production and sales volumes among polymer materials, is widely applied to a number of fields such as architecture, traffic, aviation and aerospace, national defense and military industry, etc., and plays a very important role in national economy and social development. Taking building materials as an example, PVC is more energy efficient during the process of production and usage in comparison with traditional materials, therefore PVC doors and windows have been popularized around developed western countries for a long time, and PVC ranks as highly recommended chemical building material for usage in China. Currently, there are mainly two production processes of PVC raw materials, i.e., “ethylene method” and “acetylene method”. The route of “ethylene method”, broadly used in the vast majority of countries around the world, has a limited development in China because of resource structure features of being “lack of oil, poor in gas and rich in coal”. Instead, the “calcium carbide acetylene method”, also named as “calcium carbide method”, becomes a principal method in China, by means of which the produced PVC currently accounts for about 80% of the nationwide total output. The advantages and disadvantages of the above mentioned two traditional process routes for PVC production are respectively set forth in brief as follows:
In the process route for PVC production by calcium carbide method, coal, limestone and hydrogen chloride are used as raw materials. Coke and limestone are reacted to yield calcium carbide in high temperature melting state, and then calcium carbide is reacted with water to generate acetylene gas. Through an additional reaction between the resulting acetylene and hydrogen chloride, vinyl chloride (VCM) is generated, which is finally polymerized to obtain PVC, as shown in the process procedure thereof in FIG. 1. It is well-known that the production of calcium carbide involves in high energy consumption, and meanwhile the production of VCM monomer by calcium carbide method for PVC requires to use mercuric chloride catalyst as a catalyst, with about 1.2 kg of mercury catalyst consumed for producing per ton of PVC. Accordingly, for producing 10 million tons of PVC, about 12 thousand tons of catalyst will be consumed, which requires an input of 1.32 thousand tons of mercuric chloride. Thus, this route will cause problems of both high energy consumption and high contamination.
The process route for PVC production by ethylene method takes ethylene as raw material, and commonly uses ferric trichloride as a catalyst. Ethylene and chlorine are reacted in gas or liquid phase to generate dichloroethane, which is pyrolyzed in the pyrolyzer into vinyl chloride and hydrogen chloride, wherein the hydrogen chloride is recycled by reacting with ethylene and oxygen to generate dichloroethane again, and the vinyl chloride is polymerized to generate PVC. This method, named as ethylene-oxychlorination method, becomes the most widely used production method for PVC around the world, as shown in the process procedure thereof in FIG. 2. Ethylene method for PVC production has advantages in low contamination and relatively low energy consumption, but indispensably depends on petroleum resources, further involves in huge investment on equipments and high production cost.